Which among the following halogens does not form a polyhalide ion?

What is the color of the solution when iodine is dissolved in $CCl_4$?

Assertion : Fluorine exists only in $-1$ oxidation state.
Reason : Fluorine has $2s^2 2p^5$ configuration.

Which of the following statements is incorrect?

Aqueous solution of which of the following acids cannot be kept in a bottle of glass?

When a mixture of solid $NaCl$ and solid $K_2Cr_2O_7$ is heated with concentrated $H_2SO_4$,orange-red vapours are evolved. These vapours are of which compound?